Composer is a tool for dependency management in PHP. It allows you to declare the dependent libraries your project needs and it will install them in your project for you.

The problem that Composer solves is this:
a) You have a project that depends on a number of libraries.
b) Some of those libraries depend on other libraries.
c) You declare the things you depend on.
d) Composer finds out which versions of which packages need to be installed, and installs them (meaning it downloads them into your project).

System Requirements:
Composer is multi-platform and we strive to make it run equally well on Windows, Linux and OSX.Composer requires PHP 5.3.2+ to run.

NOTE:For many operation composer depends on Git, so make sure you have git installed on your system. For windows platform make sure Git is on your environment path, and git is available on command prompt.

Installation – Linux or *nix Platform

To actually get Composer, we need to do two things. The first one is installing Composer (again, this means downloading it into your project):

$ curl -sS https://getcomposer.org/installer | php

This will just check a few PHP settings and then download composer.phar to your working directory. This file is the Composer binary. It is a PHAR (PHP archive), which is an archive format for PHP which can be run on the command line, amongst other things.

Installation – Windows

Download and run Composer-Setup.exe, it will install the latest Composer version and set up your PATH so that you can just call composer from any directory in your command line.